This invention relates generally to mobile refrigeration units and, more particularly, to a sound attenuation method and apparatus for a refrigeration unit powered by an internal combustion engine.
One well known method of transporting perishable goods is by way of a truck or trailer having a container which is refrigerated by way of an attached refrigeration unit. The refrigeration unit has an internal evaporator coil portion and an external portion that contains a condenser coil, a compressor, and an engine for driving the compressor. Since the engine is relatively loud when operating, it is important to suppress the sound from emanating to the surrounding area as much as is practicable. This is particularly true such as when, for example, the truck/trailer is parked for the night, since the truck/trailer may be in a residential or otherwise populated area.
In such a refrigeration system, there are commonly two methods for limiting the sound emanating therefrom. First, the compartment containing the internal combustion engine is closed as much as possible from the outside, and sound attenuating material is placed at various locations within the containing structure. Secondly, in order to attenuate the sound of air passing to the intake manifold of the engine by way of the air cleaner, a resonator is provided. A resonator is typically a cylindrical shaped xe2x80x9cdead air spacexe2x80x9d or tin can that is fluidly connected to the intake manifold, and is placed somewhere in the containing structure. Whereas the particular location is not important, there is a desire to conserve and effectively use the available space within the containing structure.
It is therefore an object of the present invention to provide an improved sound attenuation system for a mobile transport refrigeration system.
Another object of the present invention is to provide a suitable structure for attenuating both the sound of an internal combustion engine and the sound of air entering the inlet manifold thereof.
Another object of the present invention is the provision for effectively using the available space and for reducing the number of components included in the sound attention component.
Briefly, the objects of the present invention are attained by the use of a single structure that combines the elements of a resonator and a sound attenuating wall in one extremity of the containing structure. In this way, the available space is very effectively used and the number of components is reduced.
In the preferred embodiment of the invention, a single plastic component is formed of both a tubular resonator portion located in a plane, and a planer portion is integrally attached to the resonator so as to form an extension thereof in the same plane.
In accordance with a further aspect of this invention, the single component is comprised of a resonator portion and a planer portion. The two plastic halves are vacuum molded together to form the final single component that is placed in one wall of the containing structure for the outdoor unit.
The above, and other objects, features and advantages of the present invention will become more apparent from the following description when read in conjunction with the accompanying drawings.